Embodiments of the inventive concepts relate to integrated circuit devices, and more particularly, to integrated circuit devices with buried word lines.
As the degree of integration of an integrated circuit device constituting a buried channel array transistor (BCAT), in which a plurality of word lines are buried in a substrate, is increased, the pitch of the plurality of word lines is gradually reduced and a gate induced drain leakage (GIDL) current is increased, which may adversely affect refresh characteristics of the integrated circuit device. Accordingly, in order to suppress the GIDL current and precisely control a threshold voltage of a gate electrode, techniques for employing different kinds of materials having different work functions as components of the gate electrode have been developed. In some integrated circuit devices comprising gate electrodes including materials having different work functions, the different materials may interact with each other via diffusion. Accordingly, it may be difficult to control the work functions. Moreover, defects may be caused because of work function changes or volume expansion may occur.